Topping LA90 Review (Integrated Amplifier)

[Kitarist]

First Impressions of LA90

Application: Near field listening for media production with a Windows PC,
iMac, MOTU AVB audio network and interfaces, Rode Podcaster Pro, and
BlackMagic Mini Extreme ISO video switcher.

Speakers are Martin-Logan LX16s: Sensitivity: 92db @2.83 Volts / meter, spec'd
at 5 ohms, and a Klipsch SPL-100 Class D powered subwoofer, single ended
stereo line in.

Inputs are balanced out from a Rodecaster Pro, a MOTU Ultralite AVB, and an
A90 connected to a D90SE. All the digital audio is 48KHz/24 bit.

The LA-90 arrived via DHL in Lexington, Massachusetts coming from Shenzhen,
China. Ordered Tuesday, shipped Wednesday, received the following Monday.
Your kilometrage will vary.

During shipment the packaging received an attempted perforation, which pierced
the outer plastic wrap and entered the first layer of cardboard but didn't
pass through into the outer box. The amplifier itself lies in a bed of
form-fitted CNC'd foam inside a heavy duty dress box which in turn is
supported by styrofoam blocks at the corners. Those blocks fit neatly in the
outer box's corners, leaving an air gap of a couple of inches around the
inner box. The whole thing is sealed in a heavy waterproof plastic wrap that
is difficult(but not impossible, evidently) to penetrate. The outer box has a
small double-paned plastic window over the serial number label on the inner
box, but the plastic wrap covers it.

First LA90 impressions: very quiet, a little deaf, a little warm, very very
cute, and utterly transparent.

Very quiet: Nothing there between passages. You can tell when a microphone is
shut off in a recording mix by the drop in background noise. There's
absolutely nothing coming from the amplifier to compete with it, no matter
how high the level.

A little deaf: This amplifier expects high input levels, and deals beautifully
with hot (5 Volt!) signals. As the power amplifier for an A90 or direct from
a D90SE it delivers sufficient volume that I really must find my SPL meter.
Fed from the balanced outputs of a Rodecaster, however, it's not possible to
get loud enough to be uncomfortable. If you want loud, you have to give it
loud.

A little warm: The LA90 top surface temperature when doing normal listening
for comprehension rather than immersion runs around 93F (34C). Playing
"Another One Bites the Dust" at maximum tolerable level over and over makes
the amp hot, but you can still hold your hand on it. YMMV.

Very very cute: The front panel design and compact half rack width of this
amplifier's CNC'd aluminum chassis have a minimalist Jobsian design affect.
The front panel seems the kind of quick sketch an industrial designer would
do before figuring out the details - it has a button, a knob, and 3 LEDs. And
ironically, in the configuration I am using, the knob has been disabled, so
all that's left is that one button and 3 LEDs.

The overwhelming impression of the LA90 is transparency. I can now recognize
the slight coloration of each input device, with the A90/D90SE easily the
cleanest.

The LA90 replaced a Class D Parasound Zamp v.3 rated at 60 watts into 4 ohms.
The LA90 has less gain but is definitely capable of being much louder. The
LA90 has no discernible distortion at very high sound levels.

Biggest hassle was extracting a stereo line out for the subwoofer from the
speaker outputs. This is really only necessary if you are using the LA90's
input switch and want the subwoofer to follow that, otherwise there's a
single ended line out available on both the A90 and the D90SE. I had a couple
of single ended resistor divider networks, so I tried using them into an
isolation transformer before the subwoofer, but the sub had considerable hum.
I removed the isolation transformer and made a DC connection instead, and the
hum vanished.(I was concerned about connecting Left and Right minus out
directly to each other, hence the transformer, but it turns out they are
connected inside the LA90 anyway.)

The rear panel is crowded, as the heatsinks take out a couple of centimeters
either side, leaving around 6" by 2U for 6 x XLRs, 4 x binding posts, 1 x 64
VDC @ 4 A, 1 x USB C (firmware upgrade only), and 4 x switches.(Apologies for
the reckless use of measurement units.)

And speaking of 64V, you won't replace the custom Topping power supply at your
local surplus store. It runs slightly warmer than ambient, even when the
amplifier itself is piping hot from too much Freddy Mercury.

I am a retired television systems engineer, with 40 years experience designing
and managing the design of professional television production equipment. I
can recognize a labor of love when I see it, even if I can't hear all the
sound it makes any more (and my hearing never was great at 50 KHz). The
LA90 is not for everyone - the compact form factor drives a few inconveniences
and you won't melt buss bars with it - but someone cared very much about the
design and construction and packaging of this amplifier, it's a lovely device.

cheers,
dmc

Care to make a video?

 

[sarumbear]

@staticV3 Sorry, what I meant was 100W@8Ohm (unbridged) monoblocks capable of handling lower impedances down to 2Ohm.

Have you seen @amirm’s updated test for 2ohm load?

 

[pseudoid]

Do a search for the product and look for this:

"Operators are standing by to take your odors."...

 

[mocenigo]

The LA90 is very close to being garbage.

Please argue your point.

 

[formula 977]

Please argue your point.

No thanks. It was a personal opinion.

 

[ftlbaby]

“Equally transparent…” A blind test between this amp and the old Pro-Ject Amp Box DS, which has a similar form factor (small amp box with external SMPS) and power (from twin Hypex UcD180 modules) would be interesting.

Personally I find I hard to get excited about an amp, any amp, unless maybe it’s tiny and powerful enough to boil rocks while being so energy efficient it cools the air around it. And cheap on top of that, with super responsive meters. But hey, if a new “SINAD champ” makes others happy, cool.

"Personally I find I hard to get excited about an amp, any amp, unless maybe it’s tiny and powerful enough to boil rocks while being so energy efficient it cools the air around it. And cheap on top of that, with super responsive meters." LOLOLOLOLOLOLOL @jhaider FTW

Also, it has to be from the late 70s ; )

BTW what kind of massive rooms and speakers are you "not enough watts" folks running? And how do you still hear anything besides the ringing in your ears?

EDIT: I guess a better question: what SPL are you listening at?

 

[tomchris]

Have you seen @amirm’s updated test for 2ohm load?

I have now I know that the amplifier is superb within it's intended use and I can see that the amplifier's performance is excellent beyond its minimum load impedance specs. However, I am crossing my fingers for a future monoblock version with a larger, built-in power supply and more capacitance. I need to be able to power full range ribbon speakers .

 

[mocenigo]

No thanks. It was a personal opinion.

Yes, but based on what? Why do you "feel" it is close to garbage?

 

[pseudoid]

Yes, but based on what? Why do you "feel" it is close to garbage?

Maybe he feels he is not getting that "Bang-4-Watt" because of the price.
Give formula977 credit for replying to you frankly.

 

[mocenigo]

Maybe he feels he is not getting that "Bang-4-Watt" because of the price.
Give formula977 credit for replying to you frankly.

Judging an amplifier because of bang-4-watt is even sillier than looking at SINAD numbers and only at those.

 

[dananski]

What is the gain, or input sensitivity of your current amplifier.

It's an Arcam P39 and they list 'nominal sensitivity'. I can't find that phrase come up elsewhere in the context of amplifiers so I'm not sure what it means or if it translates to what you are asking about. Here's that section of their stats:

Inputs:

• Nominal sensitivity: 1V
• Input impedance: 10kΩ
• Maximum input: 4.6V
• Frequency response: 20Hz—20kHz ± 0.2dB
• Signal/noise ratio (Awtd) 50W, ref. 1V input: 105dB

 

[mdsimon2]

It's an Arcam P39 and they list 'nominal sensitivity'. I can't find that phrase come up elsewhere in the context of amplifiers so I'm not sure what it means or if it translates to what you are asking about. Here's that section of their stats:

Inputs:

• Nominal sensitivity: 1V
• Input impedance: 10kΩ
• Maximum input: 4.6V
• Frequency response: 20Hz—20kHz ± 0.2dB
• Signal/noise ratio (Awtd) 50W, ref. 1V input: 105dB

I assume that the signal/noise ratio spec is full power in to 8 ohm. That implies an amplifier output voltage of sqrt (50 x 8) = 20 V, so the gain is 20 x log (20 / 1) = 26 dB, so about 7 dB higher than the LA90.

Overall in terms of power output that amp seems very similar to the LA90. It is just that with a normal 2 V source you will be able to drive your current amp to full power at volume positions greater than -6 dB where as with the LA90 you will just reach about 40 W at 0 dB volume position.

What is your source?

Michael

 

[Selkirks]

Here is a size comparison with my Nord One NC500DM. I'm using the LA90 with Martin Logan Montis and Atohm GT1 speakers. Sources are Singxer SDA-6 and Topping E50. Power is not a concern so far. Initial impressions are positive with Martin Logans, in a few days I'll swap in the Atohms.

 

[Red@]

I have tested some 200 speakers. The *minimum* impedance is what I report and it is almost always in 3.6 to 4.2 ohm range. Dropping to 2 ohm is exceptionally rare. But even if it did, many people power these with amps with minimum spec of 4 ohm and don't report issues.

Regardless, I have already tested the Topping LA90 with 2 ohm load and it worked to full power in my sweep. And even pushed into clipping region for peak power measurements. So let's not continue to spread this myth.

@amirm could you please test it with a 50ohms load to simulate insensitive planars like the susvara ?

 

[dananski]

I assume that the signal/noise ratio spec is full power in to 8 ohm. That implies an amplifier output voltage of sqrt (50 x 8) = 20 V, so the gain is 20 x log (20 / 1) = 26 dB, so about 7 dB higher than the LA90.

Overall in terms of power output that amp seems very similar to the LA90. It is just that with a normal 2 V source you will be able to drive your current amp to full power at volume positions greater than -6 dB where as with the LA90 you will just reach about 40 W at 0 dB volume position.

What is your source?

Michael

It's actually 120W [per channel] at 8Ω. I'm not sure why they chose to measure SNR at 50W, but I suspect it has something to do with the class G amplification. It's class A up to 20W and suffers (slightly but audibly) as you crank it up a lot higher. The 50W could be because their top-of-the-line A49 had 50W of class A and they wanted that one to look great so they standardised their measurements around it?

I'll try to repeat the calculation... seems like voltage would be
sqrt(8*120) = 31V
Then gain is
20 log_10 (31) = 29.8 db

So the LA90 is a bit quieter as I'd expect, but I don't think I've ever gone within 10 db of maximum on the current amp. I suppose if I were to get one and find it was not quite enough, a second in bridged mode would probably sort me out.

The source is currently a Bluesound Node N100 (the original one, not that there's been any leaps in performance since). I've been trying out alternate DACs looking for a new one, but the new models have come so far they feel a bit limited by the amp (and quite probably the speakers).

Arcam P39

Oops, I meant A39. P would be the equivalent power amp, if it existed.

 

[mdsimon2]

It's actually 120W [per channel] at 8Ω. I'm not sure why they chose to measure SNR at 50W, but I suspect it has something to do with the class G amplification. It's class A up to 20W and suffers (slightly but audibly) as you crank it up a lot higher. The 50W could be because their top-of-the-line A49 had 50W of class A and they wanted that one to look great so they standardised their measurements around it?

I'll try to repeat the calculation... seems like voltage would be
sqrt(8*120) = 31V
Then gain is
20 log_10 (31) = 29.8 db

So the LA90 is a bit quieter as I'd expect, but I don't think I've ever gone within 10 db of maximum on the current amp. I suppose if I were to get one and find it was not quite enough, a second in bridged mode would probably sort me out.

The source is currently a Bluesound Node N100 (the original one, not that there's been any leaps in performance since). I've been trying out alternate DACs looking for a new one, but the new models have come so far they feel a bit limited by the amp (and quite probably the speakers).


Oops, I meant A39. P would be the equivalent power amp, if it existed.

Actually think the gain is still 26 dB (although that seems low for an integrated amplifier TBH) because they specify 50 W at 1 V input. What is slightly unclear is they don't say what impedance that 50 W is in to (4 ohm vs 8 ohm) and it seems very odd that they say 1 V input sensitivity if that only gives 50 W and max power is 120 W. Definitely a bit difficult to actually know without probably doing your own measurements.

If we take that 26 dB gain at face value and you do not go within 10 dB of max volume (and assume the Bluesound has a max output of 2 V), that gives you about 20 W in to 8 ohm so seems reasonable the LA90 would be a good fit.

Michael

 

[dananski]

Actually think the gain is still 26 dB (although that seems low for an integrated amplifier TBH) because they specify 50 W at 1 V input. What is slightly unclear is they don't say what impedance that 50 W is in to (4 ohm vs 8 ohm) and it seems very odd that they say 1 V input sensitivity if that only gives 50 W and max power is 120 W. Definitely a bit difficult to actually know without probably doing your own measurements.

If we take that 26 dB gain at face value and you do not go within 10 dB of max volume (and assume the Bluesound has a max output of 2 V), that gives you about 20 W in to 8 ohm so seems reasonable the LA90 would be a good fit.

Michael

It definitely says max power is 120W/channel into 8Ω and I remember this was a widely publicised figure, though it's interesting that you arrive at 20W since that's the A class portion of it.

Yeah, it seems a somewhat puzzling spec. I don't think there was much consistency across different companies' measurement conditions 10 years ago. Mind you, it's more detailed than Arcam's specs have become since they were taken over. I see no mention of SNR on the latest models.

I'm uncharacteristically lost on the maths here - I think I need to relearn AC stuff as I phased out during that bit of electronics . But if voltage out scales linearly with voltage in, then I think power out should be proportional to sqrt(input voltage), meaning (assuming this test was done at 8Ω) you'd reach the claimed full 120W@8Ω power output with 1.55V in (and preamp at 0dB)?

So the 2V source should be capable of hitting the A39's power limit, but I've simply never turned the preamp up enough to do this. On the LA90 you could not turn the same input up as high before hitting power limits, but you'd only be missing <10dB, and the top volumes you can get would be nice and clean.

Thanks for the assistance. I think the upshot is, as I was guessing, it'd probably be enough power for me or anyone with similar requirements. I have been meaning to buy myself a multimeter, so maybe I'll be able to check the basic numbers of my components empirically some time soon.

 

[pjug]

It definitely says max power is 120W/channel into 8Ω and I remember this was a widely publicised figure, though it's interesting that you arrive at 20W since that's the A class portion of it.

Yeah, it seems a somewhat puzzling spec. I don't think there was much consistency across different companies' measurement conditions 10 years ago. Mind you, it's more detailed than Arcam's specs have become since they were taken over. I see no mention of SNR on the latest models.

I'm uncharacteristically lost on the maths here - I think I need to relearn AC stuff as I phased out during that bit of electronics . But if voltage out scales linearly with voltage in, then I think power out should be proportional to sqrt(input voltage), meaning (assuming this test was done at 8Ω) you'd reach the claimed full 120W@8Ω power output with 1.55V in (and preamp at 0dB)?

So the 2V source should be capable of hitting the A39's power limit, but I've simply never turned the preamp up enough to do this. On the LA90 you could not turn the same input up as high before hitting power limits, but you'd only be missing <10dB, and the top volumes you can get would be nice and clean.

Thanks for the assistance. I think the upshot is, as I was guessing, it'd probably be enough power for me or anyone with similar requirements. I have been meaning to buy myself a multimeter, so maybe I'll be able to check the basic numbers of my components empirically some time soon.

Here it says the A39 sensitivity is 0.23V, so plenty of gain. (Czułość (dla maksymalnej mocy) [V] 0,23)

https://audio.com.pl/files/bhx/1901-arcam_a39.pdf

 

[solderdude]

@amirm could you please test it with a 50ohms load to simulate insensitive planars like the susvara ?

Performance will be similar or a hair better than the 8 ohm measurements so there is no need to re-test at higher impedances.
You'll be able to get 5W out of it in the Susvara = 117dB peak SPL per driver.

 

[Red@]

Performance will be similar or a hair better than the 8 ohm measurements so there is no need to re-test at higher impedances.
You'll be able to get 5W out of it in the Susvara = 117dB peak SPL per driver.

That seems very goid. But can I ask you how do you get the 5W ? Thanks
And doesn't 5w look similar to the smsl SP400 and the A90, wich in theory don't deliver as much current as to compete with an LA90 ?